Externally adjustable rotating limit switch



June 23, 1964 E. F. GOETZ 3,138,673

EXTERNALLY ADJUSTABLE ROTATING LIMIT SWITCH FIG.\

INVENTOR.

ERNEST F. GOETZ ATTORNEY Un a e Patent 0.

Filed Nov. 29, 1961, Ser. No. 155,588 4 Claims. (Cl. 200-27 This invention relates to a rotating limit switch and more particularly to a rotating limit switch externally adjustable with the shaft rotating.

A rotating limit switch is a switch with one or more contact units operated through cams on a common shaft which may be rotated through 360 or more.

The timing of the contact opening and closing commonly must be done with the shaft of the rotating limit switch at rest. With the shaft at rest the operating cams are positioned with respect to each other and the shaft positioned so that the contacts will be opened and closed at a definite point of the rotation of the shaft. The operating cams are then fastened to the shaft. After initial adjustment the shaft is rotated at its operating speed and the time of opening and closing of the contacts is checked. Usually the time of opening or closing of the contacts is somewhat late or early after the first adjustment and the rotation of the shaft must be stopped, the cams unfastened from the shaft and readjusted. This adjustment must be continued until the time of opening and closing of the contacts is exact. This continued adjustment is time consuming and tedious.

It is therefore an object of this invention to provide a new and improved rotating limit switch which a fine adjustment can be accomplished externally.

Another object of this invention is to provide a new and improved rotating limit switch capable of being adjusted while the shaft of the switch is moving.

A further object of this invention is to provide a new and improved rotating limit switch wherein each cam is capable of being externally adjusted individually while the shaft of the switch is moving.

A rotating limit switch constructed in accordance with the objects of this invention has a plurality of cams rotatable on a shaft. Each cam has a high dwell and a low dwell. A cam follower rides on each cam and is pivoted about a pivot point. A portion of each cam follower engages a contact unit to open or close the contact unit when the cam follower rides on the high dwell of a cam. The pivot point about which the cam follower pivots is movable in an arc of a circle with its center the axis of shaft about which the cams rotate. The movement of the pivot point in the arc changes the degree setting at which the cam follower actuates the contact unit.

Thus, by moving the pivot point, the degree at which the contact unit is actuated can be externally adjusted while the cams in the limit switch are moving.

The novel features of the invention are set forth with particularity in the appended claims. The invention itself, however, both as to its organization and method of operation, together with further objects and advantages thereof, may best be understood by referring to the following description and the accompanying drawings.

In the drawings:

FIGURE 1 is a view of an enclosed rotating limit switch.

FIGURE 2 is a side View of a rotating limit switch with the side enclosure removed showing one cam, one cam follower, and one contact unit.

Referring to FIGURE 1, for a better understanding of this invention, screws 3-10 may be loosened and moved in slots 1320 respectively to adjust the degree at which eight individual contact units are opened and closed. Shaft 22 is rotated to rotate eight individual cams in the 3,138,673 Patented June 23, 1964 ICC enclosure 24 to open and close eight individual contact units. Trimming adjustments may be made without removing the enclosure 24, in a manner which will become apparent. Cover 77 may be removed to gain access inside the rotating limit switch by removing four screws 25-28.

In FIGURE 2, the end enclosure of the limit switch has been removed to illustrate the internal structure. Cam 29 is secured to a shaft rotatable in a bearing in each end of the enclosure and not shown in FIGURE 2. Cam follower 31 pivots about a pivot pin 41 and cam follower roller 43 secured to cam follower 31 rides the high dwell 37 and low dwell 39 of cam 29 as the cam 29 rotates. A pivot pin support plate 45 is formed to accommodate pivot pin 41 and is secured to pivot support plate 47. Bias spring 49 is secured between pivot pin support plate 45 and pivot support plate 47 and hooked onto cam follower 31 to bias cam follower 31 in a counterclockwise direction.

Plate 50 is supported by two brackets 51 and 53 which are secured to each end of the enclosure by screws. Adjusting screw 55 screws into pivot support plate 47 through a slot 57 in plate 50. Pivot support plate 47 is thus supported by plate 50. Pivot support plate 47 and plate 50 both are shaped to form an arc of a circle with their centers being the axis of shaft 35. Thus by moving adjusting screw 55 in slot 57, pivot pin 41 may be moved in an arc of a circle about the shaft 35.

Contact unit 33 is secured to brackets 59 and 61 by screws 63 and 65 respectively. Brackets 59 and 61 are secured to the ends of the enclosure of the limit switch.

Contacts 67 and 69 are closed by contact strip 71 when plunger 73 is released and opened when plunger 73 is depressed.

Cam roller 43 rides the high and low dwells of cam 29 as the cam 29 rotates. When cam roller 43 rides the high dwell 37, as shown in FIGURE 2, contact unit engagement plate 75 secured to cam follower 31 depresses plunger 73 opening contacts 67 and 69. Contact unit engagement plate 75 is formed so that its surface is an arc of a circle with its center. being shaft 35 when cam roller 43 rides on the high dwell 37 of cam 29. The plunger 73 is thus depressed the same amount so long as cam roller 43 rides the high dwell.

The length in degrees of the contact unit engagement plate 75 is approximately the same as the length in degrees of the adjustment slot 57. Contact unit engagement plate 75 is secured to cam follower 31 so that by moving adjusting screw 55, the contact unit engagement plate 75 is moved the same number of degrees. Thus, by moving the adjustment screw 55 in the adjustment slot 57, the degree at which the contact unit engagement plate 75 depresses and releases the plunger 73 may be varied and adjusted as the shaft rotates.

The fine adjustment of the timing as described is within approximately 20. The rough timing may be accomplished by adjusting the cams 29 on the shaft 35.

Cover 77 may be removed by unscrewing screws 25-28 and removing the cover. By unscrewing the screws holding bracket 51 and loosening the screws holding bracket 53 the plate 50 may be pivoted in a clockwise direction removing the cam follower 31 and those elements afiixed to it from the interior of the limit switch. The interior of the limit switch is thus exposed for work within the limit switch, yet the cam followers may be easily replaced for operation without any change in the cam follower adjustments.

While this invention has been explained and described with the aid of a particular embodiment thereof, it will be understood that the invention is not limited thereby and that many modifications will occur to those skilled in the art. It is therefore contemplated by the appended 55 claims to cover all such modifications as fall within the scope and spirit of the invention.

What is claimed is: l. A rota-ting limit switch comprising an enclosure, a shaft rotatable in said enclosure, a cam having a high dwell and a low dwell rotatable with said shaft, pivot means, a cam follower pivoted on said pivot means for riding said cam, a contact unit secured to said enclosure to engage said cam follower when said cam follower rides the high dwell of said cam, and means for moving said pivot means in an arc of a circle with its center being said shaft to change the degree at which said contact unit engages said cam follower.

2. A rotating limit switch comprising an enclosure, a shaft rotatable in said enclosure, a cam having a high dwell and a low dwell rotatable on said shaft, pivot means, a cam follower pivoted on said pivot means for riding said cam, a contact unit secured in said enclosure, contact unit engagement means secured to said cam follower to engage said contact unit when said cam follower rides-the high dwell of said cam, and means for moving said pivot means in an arc of a circle with its center being said shaft to change the degree at which said contact unit engagement means activates said contact unit.

3. A rotating limit switch comprising an enclosure, a shaft rotatable in said enclosure, a cam having a high dwell and a low dwell rotatable on said shaft, pivot means, a cam follower pivoted on said pivot means for riding said cam, a contact unit secured in said enclosure, contact unit engagement means secured to said follower having a surface formed as an arc of a circle with its center being said shaft when said cam follower rides the high dwell of said cam to actuate said contact unit when said cam follower rides the high dwell of said cam, and means for moving said pivot means in an arc of a circle with its center being said shaft to change the degree at which said contact unit engagement means actuates said contact unit.

4. A rotating limit switch comprising an enclosure, a shaft rotatable in said enclosure, a cam having a high dwell and a low dwell rotatable on said shaft, pivot means, a cam follower pivoted on said pivot means, a cam roller rotatable on said cam follower for riding said cam, means for biasing said cam roller toward said cam, contact unit engagement means secured to said follower having a surface formed as an arc of a circle with its center being said shaft when said cam follower rides the high dwell of said cam to engage said contact unit when said cam follower rides the high dwell of said cam, and means for moving said pivot means in an arc of a circle with its center being said shaft to change the degree at which said contact unit engagement means actuates said contact unit.

References Cited in the file of this patent UNITED STATES PATENTS 1,935,124 Leeson et al Nov. 14, 1933 2,578,632 Miller Dec. 11, 1951 2,644,047 Leonard June 30, 1953 2,820,856 Krueger Jan. 21, 1958 2,855,476 Garrard Oct. 7, 1958 2,896,035 Harrington et al. July 21, 1959 

2. A ROTATING LIMIT SWITCH COMPRISING AN ENCLOSURE, A SHAFT ROTATABLE IN SAID ENCLOSURE, A CAM HAVING A HIGH DWELL AND A LOW DWELL ROTATABLE ON SAID SHAFT, PIVOT MEANS, A CAM FOLLOWER PIVOTED ON SAID PIVOT MEANS FOR RIDING SAID CAM, A CONTACT UNIT SECURED IN SAID ENCLOSURE, CONTACT UNIT ENGAGEMENT MEANS SECURED TO SAID CAM FOLLOWER TO ENGAGE SAID CONTACT UNIT WHEN SAID CAM FOLLOWER RIDES THE HIGH DWELL OF SAID CAM, AND MEANS FOR MOVING SAID PIVOT MEANS IN AN ARC OF A CIRCLE WITH ITS CENTER BEING SAID SHAFT TO CHANGE THE DEGREE AT WHICH SAID CONTACT UNIT ENGAGEMENT MEANS ACTIVATES SAID CONTACT UNIT. 